Lambda as a combination of methods from the Predicate interface doesn't compile if it is written as one statement

Question

What is the difference between both these ways of lambda creation? Why doesn't the first one compile?

Predicate<Integer> predicate = Predicate.isEqual(0).or(Predicate.isEqual(1));

Gives: error: incompatible types: Predicate<Object> cannot be converted to Predicate<Integer> = Predicate.isEqual(0).or(Predicate.isEqual(1));

Predicate<Integer> pred21 = Predicate.isEqual(0);
Predicate<Integer> pred22 = pred21.or(Predicate.isEqual(1));

This one works.

Answer 1

Adding <Integer> before the isEqual method call should help :

Predicate<Integer> predicate = Predicate.<Integer>isEqual(0).or(Predicate.isEqual(1));

The reason behind such compiler behavior:

• isEqual is a static generic method which returns Predicate<T> (no matter what actual type of its input parameter is), so it returns Predicate<Object> when calling the method without specifying returning type explicitly.
• or is also a static generic method, but it returns a predicate parametrized by the same type, as its input parameter (which is Predicate<Object>).